It is well-known in the art to include an acoustical vent in an earmold of a hearing aid or instrument. The acoustical vent is a sound duct or channel extending from a sound port in a tip portion of a hearing aid earmold to another sound port positioned in an end surface of the earmold so as to allow sound propagation between the otherwise occluded ear canal (when the hearing aid is mounted firmly in the ear) and the surroundings. A discussion of function, advantages and drawbacks of acoustical venting in hearing instruments can for example be found on pp. 34-41 of the January 2006 issue of The Hearing Journal “Open fitting of DSP instruments is not as simple as it may seem”.
A significant drawback of prior art vented hearing aid earmolds has been the occupation of shell or earmold surface area near the tip portion of the shell by two separate sound ports. A speaker sound port is coupled to the miniature hearing aid loudspeaker via a sound tube and a separate sound port for the acoustical vent as described above. This may be seen in e.g. EP1933589 and U.S. Pat. No. 6,920,227.
The tip portion of the earmold is particularly problematic in this context because of severe size constraints dictated by the requirement of fitting deeply into a user's ear canal at a position proximate to the eardrum. While the size constraints to a certain extent depend on a style of the particular hearing aid or instrument in question, such as In-the-Ear (ITE), In-the-Canal (ITC), Completely-in-Canal (CIC) or Receiver-In-Canal (RIC), it remains generally favourable to minimize occupation of shell area by the sound ports. Savings in shell area can be allocated to alternative improvements in the hearing aid design, for example, increasing the size of the miniature loudspeaker or including a cerumen barrier or an occlusion sensor etc.
The drawback has been overcome by the provision of a hearing aid earmold that comprises an acoustical duct or vent shaped and sized to transmit sound between a distant tip portion and a proximal end portion of the earmold and wherein the acoustical vent extends through a front chamber of a miniature loudspeaker or speaker of the hearing aid. This means that the acoustical vent and the speaker outlet sound channel are combined into a single common sound channel or duct needing only a single sound output port at the tip portion of the hearing aid earmold.
A hearing aid having a set-up resembling this may be seen in EP0377074 which, however, has a normal vent but has a wider channel used for flushing the front chamber of the receiver as well as the sound output from the receiver to the sound output of the hearing aid. Under normal operation, the flushing channel is plugged and a normal sound blocking vent is used.